Wireless sound

Posted on 29 May 2012


There are a lot of options out there, the cheaper single transmitter/receiver only options are:

  • E 150. ROWA RW2400 system  2.4 GHz. 5V USB, rechargeable accu. Mic in and line in (both stereo!). Headphone out + Line out. Diversity, digital. 68x46x15 mm, 70 gram, RF output power: 50mW, RF mute function, 14 channels. Autoscan manual (!?).
    > no cable lock? > is 2,4 GHz reliable (with wifi, bluetooth and microwave at the same frequency)? > is there a pre-mic limiter and low cut?), TX battery status at the RX?
    It’s like the Line 6 XD V75R 2.4 GHz digital (E 400 each, but not mobile).  Latency:  2.9 ms.
  • E 260. Samson AirLine Micro. USB power + 8hr rechargeable accu. diversity, 3.5mm mic input (5 levels + -15dB attenuator) with cable lock. Output 3,5 mm mic level (-30dBv) /line (-10dBv) unbalanced (NO cable lock!). tone-key with auto-mute. 60mm x 42.5mm x 15mm, 42 grams. Really small, light. No screen: two lights on the front of RX (battery, TX off (yellow) TX pilot OK (green) or TX overload (red)) and one on top of TX (
    Disadvantages: Only has 4 bands (!!) in Europa: 863.125 MHz, 863.625 MHz, 864.500 MHz, 864.875 MHz (also: 642.375 MHz / 642.875 MHz /644.125 MHz / 644.750 MHz / 645.500 MHz / 645.750 MHz, not Europe? Only 10 mW RF output. No headphone out. Found it at bax-shop.nl. Might be good, might be not.
  • E 528 (B&H) Sennheiser EW122-p G3. The 2nd Diversity antenna is in the cable. Not very handy I think. Screen is in front of the receiver (not handy in sound-bag). Lot’s of bands to choose.
  • E 340 (B&H) Sony uwp-v1. Non-removable, but hard antenna’s look very professional, but could potentially be damaged very easy when transporting. Screen is on front of the receiver, not handy in bag.
  • $ 300 Azden 310LT.
  • € 1795 – Micron Explorer. Nice, but very ugly. You can read the TX battery status on the RX display, which is very nice. If I was going to buy such an expensive system, I would save just a little bit more and go for Audio Ltd or better.
  • Audio Ltd – Envoy or better.  See below.
  • Sennheiser, the more expensive sets. I would go for Audio Ltd or better.

ROWA test

I’ve ordered the ROWA at dealextreme. Never buy at dealextreme again, very bad service!
But here is my review:
  • I found that the automatic channel selection doesnt work well but had a very good reception when I set both the transmitter and receiver to manual;
  • The line input of the transmitter can’t take a normal line (-10 dBV) output. It has to be attenuated a bit to work;
  • Both the transmitter and the receiver work about 3 hours on one battery (it is about 1 bar per hour on the battery indicators). The nice thing is that you can charge the battery inside of the receiver with USB from your battery pinch, so you can exchange batteries every three hours. If you need longer battery life, it could be worth it to search for  high capacity NB-4L batteries as these are 710 mAh
  • The two internal mics are not that good. Maybe nice for spying but not for recording. Also very sensitive to wind-noise.

mic input does only have very little power on it, so it doesn’t work with my DPA. What lavalier mic to use?

NB-4L battery. Available on ebay in wast quantities for about $2-3.

TX, dual RX

And then the sets where you’d only need one receiver (RX) for two transmitters (TX). The advantages are: less boxes in your bag/on your camera and the option to downmix the two to one channel if needed:

  • Cheapcheap: the € 800 dual set. I’ve heard different things about it, but most are not very positive.
  • E 1100 (at B&H). Audio Technica ATW-1821D (cost in NL: E 1437 ex VAT). TX is pretty big: 87 x 66 x 24 mm. TX also is a bit heavy: 80g without battery. Screen is top of the RX, which is good for use in audio-bag, cables are at bottom. Output High: 30 mW; Low: 10 mW, not 50 mW unfortunately. True diversity (2x receiver with 2x tuner each (4x tuner total), on 2x antenna). TX input level only in 5 steps. Internal mixdown routing. 2x mini-XLR out. headphone out. 12V power to receiver, or batteries. Automatic frequency scanning (I’ve read it’s not that reliable).  No Low Frequency cut filter and input limiter in transmitter! TX battery status on RX? They advise to use  D band (655.500-680.375 MHz).
  • € 4117 – Audio Ltd – EN2/MiniTx Dual set. Very small transmitters (2x AAA, 4,5 hours, 82  x 48 x 16.5 mm, 90g including battery). 24 MHz bandwidth. Works only with infrared remote control, which I think is not very handy. You can loose it, and if you supply a remote, do it the Lectrosonics or Zexcom way (ultrasound), so it is useful with hidden transmitters. I would say: save a little bit more. On the other hand, people are really happy with the sound quality and many say that it sounds better then the digital Lectrosonics.
  • € 4750 – Lectrosonics – Dual Set SRA-SMB. DIGITAL wireless. Small transmitters (58 x 46 x 16 mm, 95 gram). Pilot tone for TX battery status and great pre-mic amp low-cut and limiter in transmitters. Also some sort of remote control option for transmitters if they are under clothes (through ultrasound I thought). True diversity (2x tuner instead of 1x tuner on double antenna: Some manufacturers offer ‘diversity receivers’ with two antennae connected to only a single receiver. Signal switching takes place between the antennae (at rf level) which means there is often an audible ‘click’ on the recorded sound as the signal being delivered to the receiver is momentarily interrupted during switching. With the true diversity, that problem doesn’t happen since switching takes place between the two receivers at the audio frequency level with no interruption of signal.
  • € 5250 – Zaxcom – Dual TRX900LT + QRX100 set. Also very small transmitters, with recording to internal SD card in the Transmitters. Zaxcom has the ZaxNet system, a 2,4Ghz system to send TC and remote control the transmitters. GREAT! And the receiver can receive 4 (!) channels from two transmitters, with both digital and analogue outputs, and the QIFB option board for IFB audio, TC and remote control. See this article, it’s almost a smartphone! The also have a boom-operator transmitter, with IFB audio for the headphones. The only thing is that I think that the transmitters look a bit cheap compared to the Audio Ltd and Lectrosonics.

Personally, I love the sound and the limiters of the Lectrosonics. But I am interested to see the quality of the cheap digital 2,4 GHz system or the Audio Technica dual receiver.


The standard microphone of these sets often is not very good. The good choices are Rode (really!), Tram, Sanken, Countryman B6 or DPA. Think about € 300 each. Personally, I would go for Rode (cheap but good), DPA (versatile) or Countryman (good reviews!).

The annoying thing seems to be that every microphone and transmitter utilize their own plugs, like minijack, Sennheiser Lemo, Micron Lemo, Zaxcom Lemo, Lectrosonic miniXLR, Audio Technica Hirose etc etc.


For me, the important things are:

  • a pilot tone for powering off, and as I know from Lectrosonics, this pilot-tone can also send battery status information from the TX to the RX.
  • good antenna’s (so you can easily store your equipment away or adjust your antennas, without worrying about breaking anything).
  • external power options, at least for the RX but it would be nice to have it for the TX as well (when hooked to the boompole for example).
  • good limiter and pre-amp (manual levels) in the TX. good output (manual levels!) in the RX.
  • decent plugs, like lemo or xlr

And of course it would be nice of things could handle some water, cold etc and if the batteries would last forever.


There are a few 2.4 GHz systems, that are in the *free* band like bluetooth, WLAN and microwaves. You can do a lot in this band, as long as you stay under 50mW. Could not be the best thing for reliability. Also, this high frequency is more prone to directional problems then the professional 400-900 MHz systems.

On this lower band, there are different rules. You can use your transmitters at certain frequencies and certain power-levels without a permit, depending on local rules. For instane, FCC (America) has recently regulated the 700+ MHz band for public safety.

The dutch rules about channels are also changing as the government is selling frequencies to mobile internet operators. The channels from 470-862 MHz are at this moment open for professional use without a permit, except for the 608-614 MHz band (this is for radio astronomy and big events with a permit). The government is selling the 790-820 MHz and 832-862 MHz bands, which will be a no-go area from end 2015 (and may become very polluted with mobile internet from 2013).


For DSLR use it would be great to have WLAN or Bluetooth remote controlled camera’s and small mono SD cardrecorders, so you can start/stop your camera and recorders at the same time using a nice remote button on the handles of your rig. WLAN and bluetooth allow the recorders to send back an acknowledgement (that they actually start recording) and to send/receive sync data like timecode, beeps or any other things that can be written to the audiotrack of the camera. It even allows for (low/high) quality sound return from the recorder(s) to headphones for quality control, be it with a delay. This should be a nice and cheap system, because it rules out the need for transmitter, receivers and external recorders.

Something like this could be done already with the Zaxcom ZFR200 together with the Ambient LockIt, but this will be a € 2500 kit, so not exactly low-budget. And you won’t even have the confidence of monitoring the sound of the Zaxcom recorders. If they’d add sound monitoring through their ZaxNet, this might become a really great alternative. Maybe they should hook it up to the € 1090 teradek cube 220 system?

Posted in: Audio, Gear, GH2